package org.apache.lucene.store;

/**
 * Copyright 2004 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.io.IOException;

/**
 * A memory-resident {@link IndexOutput} implementation.
 *
 * @version $Id: RAMOutputStream.java 381429 2006-02-27 20:17:01Z cutting $
 */

public class RAMOutputStream extends BufferedIndexOutput {
    private RAMFile file;
    private int pointer = 0;

    /** Construct an empty output buffer. */
    public RAMOutputStream() {
        this(new RAMFile());
    }

    RAMOutputStream(RAMFile f) {
        file = f;
    }

    /** Copy the current contents of this buffer to the named output. */
    public void writeTo(IndexOutput out) throws IOException {
        flush();
        final long end = file.length;
        long pos = 0;
        int buffer = 0;
        while (pos < end) {
            int length = BUFFER_SIZE;
            long nextPos = pos + length;
            if (nextPos > end) { // at the last buffer
                length = (int) (end - pos);
            }
            out.writeBytes((byte[]) file.buffers.elementAt(buffer++), length);
            pos = nextPos;
        }
    }

    /** Resets this to an empty buffer. */
    public void reset() {
        try {
            seek(0);
        } catch (IOException e) { // should never happen
            throw new RuntimeException(e.toString());
        }

        file.length = 0;
    }

    public void flushBuffer(byte[] src, int len) {
        byte[] buffer;
        int bufferPos = 0;
        while (bufferPos != len) {
            int bufferNumber = pointer / BUFFER_SIZE;
            int bufferOffset = pointer % BUFFER_SIZE;
            int bytesInBuffer = BUFFER_SIZE - bufferOffset;
            int remainInSrcBuffer = len - bufferPos;
            int bytesToCopy = bytesInBuffer >= remainInSrcBuffer ? remainInSrcBuffer : bytesInBuffer;

            if (bufferNumber == file.buffers.size()) {
                buffer = new byte[BUFFER_SIZE];
                file.buffers.addElement(buffer);
            } else {
                buffer = (byte[]) file.buffers.elementAt(bufferNumber);
            }

            System.arraycopy(src, bufferPos, buffer, bufferOffset, bytesToCopy);
            bufferPos += bytesToCopy;
            pointer += bytesToCopy;
        }

        if (pointer > file.length)
            file.length = pointer;

        file.lastModified = System.currentTimeMillis();
    }

    public void close() throws IOException {
        super.close();
    }

    public void seek(long pos) throws IOException {
        super.seek(pos);
        pointer = (int) pos;
    }

    public long length() {
        return file.length;
    }
}
